Update README.md

Include SNMP raw data details.
Signed-off-by: Roger Pueyo Centelles <rpueyo@ac.upc.edu>

README.md

@@ -429,6 +429,41 @@ $ curl localhost:3000/map/list/device-26932/rawping/2019-03-14/23-55-00-a45632
 ```
 where the 5 first numbers correspond to the ping RTT, in nanoseconds, and the last one to the TTL count.
 
+##### device-i (bucket) => rawsnmp (map)
+The `rawsnmp` *map* in the `device-i` *bucket* is a collection of nested maps where the raw SNMP data are stored.
+
+The following call will not work<sup>2</sup>, but gives an example of the data structure:
+```bash
+$ curl localhost:3000/map/list/device-26932/rawsnmp/
+  {["2018-12-31","2019-01-01","2019-01-02","2019-01-03","2019-01-04","2019-01-05","2019-01-06", ... ,"2019-03-13","2019-03-14"]}
+```
+
+##### device-i (bucket) => rawsnmp (map) => year-month-day (map)
+The `year-month-day` *map* in the `rawsnmp` *map* in the `device-i` *bucket* contains the raw SNMP data stored during a given day.
+
+The following call will not work<sup>2</sup>, but gives an example of the data structure:
+```bash
+$ curl localhost:3000/map/list/device-26932/rawsnmp/2019-03-14/
+  {["00-00-00-21435","00-00-00-a45632","00-00-00-a47363","00-05-00-21435","00-05-00-a45632","00-05-00-a47363","00-10-00-21435","00-10-00-a45632","00-10-00-a47363","23-50-00-21435","23-50-00-a45632","23-50-00-a47363","23-55-00-21435","23-55-00-a45632","23-55-00-a47363"]}
+```
+
+##### device-i (bucket) => rawping (map) => year-month-day (map) => hour-minute-second-monitorID (set)
+The `year-month-day` *map* in the `rawsnmp` *map* in the `device-i` *bucket* contains the raw SNMP data captured at a given moment by a specific monitor.
+
+The following call will not work<sup>2</sup>, but gives an example of the data structure:
+```bash
+$ curl localhost:3000/map/list/device-26932/rawsnmp/2019-03-14/23-55-00-a45632
+  {["sfp1", "0", "320", "ether1", "0", "0", "wlan1", "72752170", "194023223",
+  "ether3", "4211890690", "3457835469", "ether4", "1481996123", "3715009965",
+  "ether5", "3986712032", "2292081157", "ether6", "6036", "43256812", "wlan5",
+  "3253125075", "4192397953", "wlan6", "1438160383", "430948927", "ether9", "0",
+  "0", "ether10", "0", "0", "lan", "75134070", "158936718", "wlan2", "0", "0",
+  "wlan3", "1224542542", "3312721186", "wlan4", "0", "6703436", "sjd",
+  "166864741", "6605882", "bel", "0", "6605882", "qmp", "0", "0", "wlan7",
+  "2064155005", "1601779739"]}
+```
+where the data are ordered, sequentially, as "Interface name", "RxBytes", "TxBytes", etc.
+
 ---
 <sup>1</sup> LWW: last writer wins  
 <sup>2</sup> The REST API does not support nested maps (but the Go client does)